Nile sediment dispersal altered by the Aswan High Dam: The kaolinite trace

Proportions of kaolinite have increased substantially in lower River Nile clay mineral assemblages since emplacement in 1964 of the High Dam at Aswan, Egypt. Monitoring this recent increase can be used to help gauge sediment load changes induced by the High Dam in the lower River Nile, between the dam and Nile delta and, eventually, offshore in the Mediterranean's Levantine Basin. High kaolinite values (to 50%) are recorded north of the new Nile delta presently forming in Lake Nasser, and are even higher below the High Dam (to 70%). Kaolinite is introduced to Lake Nasser from adjacent desert terrains largely from wind transported material and wave erosion of lake margins. As the major clay component of the suspended sediment load in lake waters, this mineral is released through the dam. Additional kaolinite enters the Nile system just below the High Dam from late Pleistocene and older sections scoured by swift, turbulent Nile waters flowing northward of the dam. During the past 31 years, sediment containing higher concentrations of kaolinite (similar to 30%) has migrated northward at a rate of similar to 10 km/year, and presently extends to Qena similar to 350 km north of the dam; this stretch defines the River Nile sector most altered since closure of the High Dam. It is predicted that enhanced proportions of kaolinite will be recorded at Cairo and the southern Nile delta within 50 years, and at the Mediterranean coast by the end of the next century.